Flexible and Low-cost Interface Circuit for Electrochemical and Resistive Gas Sensors

This work presents a low-cost interface circuit for both electrochemical and semiconductor sensors for gas detection. The proposed circuit offers a high sampling rate, on the order of 25 ms, allowing the monitoring of the sensor behaviour even in presence of fast transients. The front-end has a single-voltage 3.3 V power supply and a time-coded digital signal output, thus it is suitable to be directly interfaced to a microcontroller for the management of the measurement process. Possible integration in a single-chip solution, together with the digital electronics is furthermore facilitated. Experimental results, conducted on a discrete component prototype and with sample resistors to emulate the sensor, have shown a maximum linearity error in the estimation of the sensor current or resistance of about 5% over a measurement range of seven decades, demonstrating the validity of the proposed solution. The power dissipation of the front-end is less than 30 mW (at 3.3 V) and the front-end cost less than 10 EUR, making it suitable for the employment in low-cost and low-power gas detection systems.